DocSolarisReich
Esoteric Spaceman
That's not what rational means in the context of economics. Economists do not typically look at Harry Potter and the Methods of Rationality and think: "Hmm, yeah this is a good behavioral framework to base our theories of society on."
In economic theory "rational" simply means that if people want something, they will try to obtain that something. If that something costs more than to get than they are willing to pay, they will not get it, but if the price is lower than they are willing to pay, they will do so. Most humans will exhibit this sort of behavior to enough of a degree to make economic theory work.
And we're back to our homo economicus.